UPDATE (10:01 a.m.): DDOT says the the tunnel has been completely reopened.
D.C. Fire & EMS says nothing hazardous was found.
ORIGINAL STORY: D.C. Police are investigating an unattended dump truck inside the 3rd Street tunnel.
Police say they came upon the suspicious vehicle just after 8:30 a.m.
Northbound traffic into the tunnel is being affected the investigation.